排序方式： 共有42条查询结果，搜索用时 151 毫秒
1.
N. R. Krishnaswamy 《Resonance》1996,1(2):40-46
Chemical methods to determine the conformations and absolute configurations of menthol, a cyclohexane derivative with 3 chiral centres, are described. 相似文献
2.
N R Krishnaswamy 《Resonance》1996,1(7):23-30
Some interesting examples of the linkage between the structure and biological function of secondary metabolites in plants and animals are described. 相似文献
3.
Droplet-based microfluidics has gained extensive research interest as it overcomes several challenges confronted by conventional single-phase microfluidics. The mixing performance inside droplets/slugs is critical in many applications such as advanced material syntheses and in situ kinetic measurements. In order to understand the effects of operating conditions on the mixing performance inside liquid slugs generated by a microfluidic T-junction, we have adopted the volume of fluid method coupled with the species transport model to study and quantify the mixing efficiencies inside slugs. Our simulation results demonstrate that an efficient mixing process is achieved by the intimate collaboration of the twirling effect and the recirculating flow. Only if the reagents are distributed transversely by the twirling effect, the recirculating flow can bring in convection mechanism thus facilitating mixing. By comparing the mixing performance inside slugs at various operating conditions, we find that slug size plays the key role in influencing the mixing performance as it determines the amount of fluid to be distributed by the twirling effect. For the cases where short slugs are generated, the mixing process is governed by the fast convection mechanism because the twirling effect can distribute the fluid to the flow path of the recirculating flow effectively. For cases with long slugs, the mixing process is dominated by the slow diffusion mechanism since the twirling effect is insufficient to distribute the large amount of fluid. In addition, our results show that increasing the operating velocity has limited effects on improving the mixing performance. This study provides the insight of the mixing process and may benefit the design and operations of droplet-based microfluidics. 相似文献
4.
We report a case of a diabetic, heterozygote with near normal hematology, marginally low level of hemoglobin A2(HbA2) having an increased level of hemoglobin F(HbF) that was pancellularly distributed among the red cells. BioRad DiaSTAT measurements
gave a high glycated hemoglobin A1c(HbA1c) of 31.5% and the BioRad Variant analyzer recorded an HbA1c value which was very
low, in discordance with the detected blood glucose levels. Flow cytometry and polymerization chain reaction (PCR) based studies
were carried out which revealed the case to be that of the common hereditary persistence of fetal hemoglobin (HPFH)-3, an
Asian Indian mutation. Fructosamine estimation and HbA1c by Boronate affinity chromatography were able to resolve the discordant
value detected and was able to confirm the diabetes status. The case would have been a diagnostic dilemma, if reported without
correlation. 相似文献
5.
6.
Analyzing examinees’ responses using cognitive diagnostic models (CDMs) has the advantage of providing diagnostic information. To ensure the validity of the results from these models, differential item functioning (DIF) in CDMs needs to be investigated. In this article, the Wald test is proposed to examine DIF in the context of CDMs. This study explored the effectiveness of the Wald test in detecting both uniform and nonuniform DIF in the DINA model through a simulation study. Results of this study suggest that for relatively discriminating items, the Wald test had Type I error rates close to the nominal level. Moreover, its viability was underscored by the medium to high power rates for most investigated DIF types when DIF size was large. Furthermore, the performance of the Wald test in detecting uniform DIF was compared to that of the traditional Mantel‐Haenszel (MH) and SIBTEST procedures. The results of the comparison study showed that the Wald test was comparable to or outperformed the MH and SIBTEST procedures. Finally, the strengths and limitations of the proposed method and suggestions for future studies are discussed. 相似文献
7.
Among the traditional five sensory perceptions, colour and smell often go hand in hand, along with taste. Among the objects used for worshipping God, for instance, flowers and incenses occupy prime places. The subject matter of this article is the chemistry of musk and related perfumes derived from natural sources. 相似文献
8.
9.
Ratna Nandakumar 《Journal of Educational Measurement》1991,28(2):99-117
This article addresses testing the hypothesis of one versus more than one dominant (essential) dimension in the possible presence of minor dimensions. The method used is Stout's statistical test of essential unidimensionality, which is based on the theory of essential unidimensionality. Differences between the traditional definition of dimensionality provided by item response theory, which counts all dimensions present, and essential dimensionality, which counts only dominant dimensions, are discussed. As Monte Carlo studies demonstrate, Stout's test of essential unidimensionality tends to indicate essential unidimensionality in the presence of one dominant dimension and one or more minor dimensions that have a relatively small influence on item scores. As the influence of the minor dimensions increases, Stout's test is more likely to reject the hypothesis of essential unidimensionality. To assist in interpreting these studies, a rough index of the deviation from essential unidimensionality is proposed. 相似文献
10.
The characteristic X-rays coming out from an unknown sample due to the irradiation of gamma rays or X-ray photons or due to
the bombardment of high velocity protons are used for elemental analysis in a sample. We describe here two techniques viz.,
Energy Dispersive X-Ray Fluorescence (EDXRF) and Proton Induced X-ray Emission (PIXE) which have the capability of nondestructive
and multi-elemental analysis of the sample.
N K Sharat Singh is a research scholar at the Department of Physics, Manipur University. His research interest lies in areas
of EDXRF and PIXE.
H Nandakumar Sarma is a professor of physics at Manipur University. His current research focuses on EDXRF, PIXE, ferroelectric,
ferrite, Mossbauer effect and solar energy. He occasionally writes popular science articles both in English and Manipuri.
An erratum to this article is available at . 相似文献